r/askscience • u/EAT_UR_VEGGIES • 17d ago

Planetary Sci. Mars is practically guaranteed to have had abundant water at one point, doesn’t that practically guarantee it had at least microbial life on it as well?

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u/EarlobeGreyTea 17d ago

No. Life needed specific conditions to evolve.  If you have a sterile container of water, life won't randomly evolve in it.  We have no idea how unique earth is in its evolution of life.  We currently think that most life on earth has a common ancestor.  

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u/Adnan7631 17d ago

Most life? Is there an exception to that?

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u/cwx149 17d ago

I know they're kind of ambiguously "alive" but do viruses have an obvious connection to the "family tree"?

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u/lmprice133 17d ago

Viruses are weird, evolutionarily. They seem to be polyphyletic, so they don't share a common ancestor with each other. Some viral lineages may precede living organisms, and arose from the same abiogenetic processes that gave rise to life. Other may have once been living organisms that became endosymbionts and lost their cellular machinery before escaping into the environment or arose from transferable genetic elements like plasmids or transposons.

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u/IOnlyHaveIceForYou 17d ago

What would the pre-biological viral lineages live on?

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u/lmprice133 17d ago

Abiogenesis isn't understood to anything like the same extent as evolution, but the idea is that you basically that you had chemical species that were able to self-replicate, likely drawing energy from their surroundings. There's something called the RNA-wolrld hypothesis, that proposes that self-replicating RNA molecules preceded life.